[Resolved] Can't revert to buddybar

After recent upgrade to 1.6.4 an admin wanted to try using the wp-admin-bar so he checked the option to make that change within BP settings. He doesn’t like it, but we can’t find a way to revert. Tried the bp-custom hack, defining in wp-config and bp-config, but nothing works. Tried reverting to 1.6.1 but made no difference.
I’m assuming that setting option writes something somewhere that needs to be removed or changed, but where?